Dexter appears to have been stabbed. He seems to be bleeding from his abdomen, and in his hand is a large, bloody knife.

He phones 911 and reports that he has been stabbed, then collapses to the ground.

An ambulance arrives and the two ambulance attendants find Dexter lying face down.

But as they approach, Dexter suddenly springs to life, nailing both ambulance drivers with twin hypodermics.

They wake up inside the ambulance, parked inside the warehouse.

Turns out
that they had been letting emergency patients die, in order to supply a
crooked doctor with body parts for transplants.

Dexter kills them both (simultaneously), with the electrified paddles of a defibrillator.

Q.
What is it actually in real life?

A. A warehouse. Just not in Miami.

Q.
Where can I find it in real life?

This warehouse is located at 615 W. 17th Street (just west of Daisy Avenue), in a somewhat rough section of west Long Beach, CA. It's just south of Pacific Coast Highway, and just a couple of blocks east of the Long Beach (710) freeway.

Googling that address turns up two business names: PDF Warehouse and Southend Cartage.

In all four of the
screencaps above, the camera is behind Dexter, inside the warehouse
yard, looking south out the gate, onto 17th Street.

The intercut shots of the ambulance racing to the warehouse were filmed miles away, in San Pedro, CA. The ambulance is racing north up Signal Street, just north of Trinity's Warehouse and the dock where Dexter killed Liddy.

The
warehouse doors you see behind the ambulance belong to an extremely long
warehouse that runs along the west side of Signal Street, and which was
where they built the Mexican tunnels for the 2009 movie, "Fast & Furious". (I've been on Signal Street several times, and recognized those warehouse doors.)

A. In previous seasons, I've
usually had to hunt down the locations after viewing the episodes,
using clues from the various scenes. By the 6th season, though,
I'd developed a small group of fans, spies & tipsters who kept an
eye out for Dexter filming in their neighborhoods, and would let me know
in advance when something was about to film there.

Between those reports, my own personal reconnaissance around town, and a
few new resources I discovered, by the time the first episode aired, I
already knew most (but not all) of the filming locations, and only
needed to watch the episodes and match up the scenes with the correct
locations.

This group of helpful fans includes Kerry, Rick, Ellen, Susan, Joel, Julie, Geoff,Jeff, and others. My thanks to all of them.

This time, Rick tipped me to the
fact that they were shooting somewhere in the warehouse area around Daisy & 17th.

When the scene aired, at first I thought it was Tempco (the location
used as Mos Def's garage). But upon closer inspection, I realized it
wasn't, so I went looking around Daisy & 17th, via Google
StreetView. Sure enough I quickly found a view that was a perfect match for the scene, right down to the broken pavement and the piles of trash bags. (Thanks, Rick!)